Tests on the patented Rotho-Noxys system controlled by Dr. Fulvio Mattivi of the Mach Foundation, Centre for Research and Innovation, Food Area, San Michele all’Adige Trento.
In-house testing was performed with the help of oenologist Mario Pojer at the Azienda Agricola Pojer & Sandri, in Faedo (TN), during the 2009 wine harvest.
The varieties chosen were Traminer Aromatico (TA), Muller Thurgau (MT) and Sauvignon Blanc (SB).
Each batch of grapes was randomised, chilled and divided into two lots using procedures aimed at obtaining a nitrogen processing atmosphere with levels of oxygen equal to or less than 1%.
Each variety was crushed, comparing feeding using the Rotho-Noxys with feeding of the whole grape clusters into the press.
The whole grape clusters were fed from above, inertized under vacuum and processed in nitrogen.
The grape clusters were crushed to obtain a must yield of 70%, using a programme of up to 1.8-2.0 bars.
The pumped grape crushing programme was shortened and the pressure was reduced (about 1.5-1.6 bars) until an identical must yield was obtained. Identical quantities of sulphur dioxide and ascorbic acid were used for the two tests on the same variety. The quantities used were about 3 g/quintal SO2 and 2 g of ascorbic acid per TA and MT (double for the SB).
In general, crushing pumped grapes leads to an increase in the extraction of native (non-oxidised) cinnamic acids.
For the same must yield, the content of cinnamic acids is higher with pumped grapes.
For the different processes, the cinnamic acid content of the must from pumped grapes is between 52 and 72% of the total estimated content of the grape berry.
Considering that the juice contains just a minor fraction (between 24 and 37%) of the cinnamic acids in the grape berry, it can be concluded that the extracted must contains all the cinnamic acids present in the grape juice, plus an important part of the compounds extracted from the pulp and skin, in the native form preserved from oxidation.
Content of cinnamic acids in the must obtained after crushing using the two different feed systems
For the same must yield, the total polyphenols content in the must obtained from pumped grapes is higher than that obtained from whole grape clusters. This increase is due partly to the greater extraction of cinnamic acids (see above) and partly (although not excessively) to greater extraction of other polyphenol compounds, catechin in particular.
Content of phenol compounds in the must obtained after crushing using two different feed systems
The importance of loading the press is particularly evident from the reduced glutathione content in the must. In the two tests with MB and SB, the concentrations of glutathione were more than 96% and 42% respectively. This result is mainly due to the greater protection during the loading phase. The differences in composition are, in fact, most evident in the free-run must.
The reduced glutathione content in the must from pumped grapes is always high, between 51 and 68% of the total content in the grape berry.
This demonstrates that 100% of the glutathione in the juice, together with a significant part of the glutathione in the skin, can be transferred to the must using this method.
Content of glutathione in the must obtained after crushing using two different feed systems
Musts from pumped grapes contain greater quantities of total and free sulphur dioxide. With the exception of TA, where free sulphur dioxide consumption was accelerated by incomplete inertization of the press, a higher content of sulphur dioxide was present at the end of crushing with SB and MT. This result is due to more effective protection from oxidation phenomena during loading of the press, with less sulphur dioxide consumption.
In practice, with more efficient press loading, less sulphur dioxide is required to guarantee the same antiseptic and antioxidant effect on the must.
Content of free and total sulphur dioxide in the must obtained after crushing using two different feed systems
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